Direct current electric motors are commonly used to drive a fan or blower in a vehicle ventilating system. Such motors have a rotating shaft which extends through a motor housing having one end carrying a first bearing or bushing supporting one portion of the shaft and an opposed end carrying an end plate. A second bearing or bushing is typically held in place in the end plate by a retainer and engages an opposed end portion of the rotating shaft.
As shown in FIG. 1, a prior art electric blower motor for a vehicle ventilating system has a fixed part formed of a generally cylindrical housing or metal body shell having a base wall at one end with an enlarged boss which receives the first bearing or bushing. An end plate is fixedly joined to the other end of the housing. Permanent magnets are mounted on the inner surface of the body shell and surround the shaft. Brushes are mounted in an electrically insulating brush holder or card which is disposed adjacent to the end plate. The brushes make contact with a rotating part or armature of the motor which is mounted on the drive shaft.
The second bearing or bushing is mounted in the end plate by means of a retainer plate. An oil throw washer, a separate wear washer and a separate isolation washer are mounted within the housing body between the armature and the second bushing. The oil throw washer is shaped to re-circulate lubricant which has been expelled from the lubricant-impregnated second bushing back toward the second bushing.
In this typical motor configuration, the oil throw washer is disposed in engagement with the commutator. The isolation washer is then interposed between the oil throw washer and the Nylatron (Nylon 6, 6) wear washer which acts as a wear surface in contact with the second bearing.
However, this design requires three separate parts which increase assembly time.
Thus, it would be desirable to provide an electric motor in which a lubricant recirculation path is formed adjacent to a lubricant impregnated bearing and wear protection and vibration dampening characteristics are obtained with fewer parts and improved performance over prior art motor designs.
The present invention is a lubricant recirculation member for an electric motor which provides multiple functions in a single unitary part.
The motor includes a housing having first and second ends. A rotatable shaft extends through the housing. A commutator is disposed in the housing about the shaft. A bushing is mounted in the housing in engagement with the shaft. The lubricant recirculation member is disposed in a housing about the shaft between the commutator and the bushing. The lubricant recirculation member is in the form of a body having a unitarily joined first lubricant recirculation end wear surface portion and a second vibration dampening portion.
The first portion of the body has an internal cavity with a sidewall shape to recirculate lubricant away from the commutator. Specifically, the first portion has a base with a wear surface engaged with the bushing. The sidewall extends non-linearly away from the base to form a pocket with the base to collect and recirculate lubricant from the bushing back toward the bushing where it is re-absorbed by the bushing.
The first and second portions of the body have complimentary, interlocking members which mechanically interlock the first and second portions together.
Preferably, the second portion of the body is formed of a thermoplastic elastomer. Specifically, in one example, the thermoplastic elastomer is polyester co-polymer.
Complimentary peripheral interlock members may be optionally formed on the first and second portions of the body. The interlock members include annular radially inward and radially outward complimentary formed members to provide added mechanical interlock between the first and second portions.
In another aspect of the invention, a plurality of circumferentially spaced fingers extend from the first portion into a central bore in the second portion. A radially innermost surface of each of the plurality of fingers engages the shaft of the motor to center the lubricant recirculation member about the shaft. The adjacent resilient material of the second portion between the fingers seals the shaft.
The lubricant recirculation member, or oil slinger, is mounted between the commutator and rear or second bushing. Any oil or lubricant excreted from bushing is returned by the oil slinger through a pocket formed in the oil slinger back to the outer surface of the bushing where it is reabsorbed. This prevents the lubricant from leaking to other electrically conductive portions of the motor interfering with efficient motor operation or causing objectionable noise.
The lubricant recirculation member, or, oil slinger, according to the present invention is formed as a single piece thereby reducing the overall cost of providing the same functions as the three separate washers in prior art motors. Thus, in a single part, the lubricant recirculation member or oil slinger of the present invention provides the function of recirculating the bushing lubricant back into the bushing system, protects the commutator from lubricant contamination, provides a vibration dampening material layer between the commutator and the bearing or bushing, and provides a wear surface between the bushing and the lubricant recirculation portion of the oil slinger.